TW201402772A - 3-dimentional electrically conductive adhesive film - Google Patents

Abstract

Provided is an adhesive film comprising a layer of an adhesive mass and conductive particles admixed in the adhesive, characterized in that a portion of the particles is fibrous conductive particles and another portion of that has a dendritic structure.

Description

Three-dimensional conductive adhesive film

The present invention describes an adhesive film for bonding two articles together for a long period of time and having electrical conductivity in three dimensions.

As electronic components become smaller and smaller, the processing becomes more and more difficult, making the soldering work of electronic components no longer simple, and the welding work cannot be completed at low cost. This makes the technology of bonding electrical and electronic components with a conductive adhesive layer more and more important. To this end, conductive pigments (e.g., carbon black), metal powders, ionic compounds, and the like are typically doped into the adhesive. There is currently a range of tapes on the market that are electrically conductive only in the z-direction (ie, in the direction of the tape) or in the z-direction and the x-y direction (ie, the plane in which the tape is located). There are many different possibilities to achieve this conductivity.

One possibility is to use an electrically conductive carrier so that the adhesive only needs to be electrically conductive in the z direction so that the entire tape is also electrically conductive in the x-y direction. The current is directed to the carrier by the adhesive, then distributed in the x-y direction, and then guided through the adhesive from the z direction To the surface.

The difficulty is how to have conductivity in the x-y direction without a carrier, that is, how to make a so-called carrierless double-sided tape.

In some applications, especially in the electronics industry, very high adhesion must be achieved with very thin layers of tape. In some cases, such as adhesion of flexible printed circuit boards, unsupported tape is often used because if the carrier is used, the adhesive layer may become too thin to achieve good adhesion strength. Another cause is that in these applications, the tape may be exposed to high temperatures, such as 288 ° C when soldering components, and only a very small number of carriers will not be melted at this temperature.

An example of a carrierless double-sided tape having conductivity only in the z direction can be found in the literature. US 3,475,213 describes spherical particles which are statistically distributed, either entirely of a conductive metal or coated with a layer of conductive metal. These particles are slightly smaller than the adhesive layer. No. 4,113,981 describes tapes coated with conductive spherical particles, wherein the particles are approximately equal in thickness to the tape and do not exceed 30% by volume of the adhesive. Other special embodiments and applications are described in US 4,606,962 and US 5,300,340. Further, if spherical particles are used so as to have conductivity in the X-Y direction, a very large amount of particles need to be added because these particles must be in contact with each other.

All of the tapes mentioned above are based on self-adhesive or heat-activated acrylate adhesives, which are adhesive adhesives, but in many applications, two adhesives are used to adhere two objects together. At the beginning, the adhesive strength required for the application is often not achieved. This situation is mainly caused by the high load (tension, shear or torsion), which will fall off after a short time of adhesion.

When a conductive particle of up to 30% by weight is added, the adhesion of the adhesive having a lower adhesion generally becomes lower. The resulting bond strength is insufficient to ensure long-term connection of electrical contacts that are subjected to mechanical loads.

Since a part of the particles are released from the surface, especially when high conductivity is required, the particles become spacers between the adhesive and the substrate to be bonded, resulting in a worse adhesion effect.

Another disadvantage of the prior art mentioned above is that the adhesive may fall off and thus require manual reinforcement.

Particularly soft components such as flexible printed circuit boards are subject to large bending stresses and are therefore particularly sensitive to adhesive failure.

DE 199 12 628 A describes a thermoplastic polymer-based tape which has a hybrid adhesive resin and an epoxy resin which reacts upon heating to cause a crosslinking reaction. As for the conductive particles, only silver particles or silver-plated particles are mentioned. However, such tapes only have electrical conductivity in the z-direction, that is to say electrical conductivity only in the direction perpendicular to the adhesive layer.

It is difficult to create a three-dimensional conductive adhesive film by spherical particles because the particles must be in contact with each other to produce conductivity on the plane, so a very large amount of particles needs to be added. However, such a high degree of filling of the conductive particles causes a significant drop in adhesion.

Therefore, the spherical particles are often replaced by dendritic particles, and in the case of the same volume, the dendritic particles have a table much larger than the spherical particles. Area, so only a small amount of conductive particles need to be added. However, this will make the surface of the adhesive rough, especially when the adhesive is made from the solution, because the "small branches" of the dendrites protrude outward from the adhesive, and the dendrites are not like spherical particles. Just as each particle has the same size, it imposes significant limitations on the lamination of the adhesive.

SUMMARY OF THE INVENTION The object of the present invention is to avoid the disadvantages of the prior art and to provide an unsupported three-dimensional space conductive tape, and that the two joined parts which are bonded for a long time with such a tape have good lamination property and high adhesive strength.

The above object can be attained by using an adhesive film which is described in detail in the scope of the patent application of the present invention.

The adhesive film of the present invention comprises a layer of an adhesive and conductive particles doped in the adhesive, one of which is a fibrous conductive particle and the other of which has a dendritic structure. According to a very advantageous way, this is an unsupported double-sided adhesive film, that is to say a single-layer, carrier-free adhesive film composed of a particulate-containing adhesive.

It is preferred to use a crosslinkable adhesive, especially if it is crosslinked when heated.

The invention is therefore preferably a thermally activated thermally crosslinked adhesive.

Adhesive

The adhesive film of the present invention contains an adhesive substrate, and the conductive particles used in the present invention are doped in the adhesive substrate, and preferably both are Evenly distributed in the adhesive substrate.

For example, a pressure sensitive adhesive having a known composition can be used as the adhesive. However, according to the present invention, a highly advantageous adhesive film has a substrate composed of a heat-activatable adhesive. Heat-activatable adhesives (also referred to in the literature and in the present invention as "heat-activated adhesives" and "heat-activated adhesives") are generally not self-adhesive or have very weak self-adhesive properties at room temperature. However, it is also possible that some heat-activated adhesives have a significant self-adhesiveness at room temperature. However, the adhesive properties required for the application will not be activated until the input heat is applied. After cooling, it creates a sticking effect, thus achieving the desired adhesion.

This specification refers to a heat activated (adhesive) film or a heat activated (adhesive) tape as a double-sided adhesive film or a double-sided adhesive tape, and the adhesive layer is composed of a heat-activatable adhesive. The heat activated film or the heat activated tape is planar before being placed on the substrate to be bonded, and in principle can be formed into a single layer or a plurality of adhesive films, wherein the multilayer adhesive film may or may not contain a carrier layer. The conductive adhesive film of the present invention is a single layer and has no adhesive film of a carrier.

When used, the heat activated film or heat activated tape is placed on the substrate to be bonded or placed between the substrates to be bonded, for example, at room temperature or above. It is then heated to activate to achieve final bonding.

In principle, heat-activated adhesives suitable as substrates for the adhesive films of the present invention can be distinguished into two major classes, namely thermoplastic heat-activated adhesives and reactive heat-activated adhesives.

a) Thermoplastic heat activated adhesive

This adhesive has no self-adhesiveness or only weak self-adhesiveness at room temperature. After heat activation, the adhesive will be self-adhesive. Since the glass transition temperature of the adhesive is quite high, the activation temperature required to achieve sufficient viscosity is usually several tens to one hundred degrees Celsius higher than room temperature. Due to the self-adhesive nature, the adhesion has already occurred before the adhesive solidifies and hardens. When the articles to be bonded are joined, the thermoplastic heat-activated adhesive will be physically cured when cooled and hardened (using a suitable thermoplastic material as an adhesive, usually resulting in reversible bonding), sometimes accompanied by chemical curing ( The use of a suitable thermoplastic reactive material as an adhesive usually results in irreversible bonding, so that it remains viscous in the cooled state and forms an intrinsic bond. The more heat, pressure and/or time used for bonding, the stronger the bond between the two materials to be bonded. This allows maximum bonding strength to be achieved with technically easy to implement processing conditions.

The term "thermoplastic" refers to a compound defined by Römpp (online edition; published in 2008, document number RD-20-01271).

b) Reactive heat activated adhesive

The term "reactive heat-activated adhesive" refers to a polymer system having a functional group which generates a chemical reaction upon heating, in which the adhesive chemically condenses and hardens, thereby causing an adhesive effect. Reactive heat-activated adhesives generally do not produce self-adhesive properties when heated, so they are sticky when coagulated and hardened. Reactive heat-activated adhesives are generally not thermoplastic, but are achieved via an elastomer-reactive resin system (please compare with a thermally activated film made of a thermoplastic-reactive material; as described above).

Glass transition temperature is not critical to the functionality of the active system Want.

In principle, the adhesive is composed of one or several polymers (basic polymer component, referred to as the base polymer). In order to adjust the properties of the adhesive, other components such as a resin (viscous resin and/or resin) are usually incorporated. Or a reactive resin), a softening agent (and other similar ingredients), if necessary, may also incorporate other additives which have a beneficial effect on the properties of the adhesive, such as fillers or conductive particles which are of considerable importance in the present invention.

The following are all examples of elastomers suitable as the base polymer of the adhesive of the present invention (particularly as an example of an elastomer of a base polymer of a reactive heat-activated adhesive): poly-α olefin, polyisobutylene, poly Isoprene, polybutadiene, amorphous polypropylene, nitrile rubber, polychloroprene, polyvinyl acetate, polyvinyl vinyl alcohol, styrene butadiene rubber, polyester, polyurethane , and / or polyamine. The best is to use nitrile rubber.

The most suitable polyurethane is a thermoplastic polyurethane (TPU) which is the reaction product of a polyesterified or polyethered and organic diisocyanate. These materials can be used as thermoplastic thermal activation systems or as thermoplastic-reactive thermal activation systems.

The above-mentioned polymers may be used singly or in combination (containing one or several other polymers).

One advantageous way is to add one or more reactive resins to the base polymer of the thermoplastic-reactive heat activated adhesive film and the reactive heat activated adhesive film (elastomer based adhesive film). The proportion of the resin to the heat-activated adhesive is preferably from 30 to 75% by weight based on the total weight of the base polymer and the reactive resin (excluding the conductive particles). between.

According to the present invention, one or several resins may be independently selected from the resins listed below as the active resin:

-- Epoxy resin; the average molecular weight M _w (average weight) is preferably between 100 g/mol and 10000 g/mol. For example, polyepoxy resin is an example of an active resin belonging to a high molecular weight range.

The following are some examples of advantageous epoxy resins: the reaction product of bisphenol A and epichlorohydrin, the reaction product of epichlorohydrin, glycidyl ester, epichlorohydrin and p-aminophenol.

The following are several examples of commercially available epoxy resin: Ciba Geigy produced ^{Araldite TM 6010, CY-281 TM} , ECN TM 1273, ECN TM 1280, MY 720, RD-2, produced by Dow Chemical Co. DER ^TM 331, DER ^TM 732, DER ^TM 736, DEN ^TM 432, DEN ^TM 435, DER ^TM 438, Epon ^TM 812, 825, 826, 828, 830, 834, 836, 871, 872, 1001 manufactured by Shell Chemicals, Inc. 1004,1031 and the like, and is also produced by Shell Chemicals company HPT ^TM 1071, HPT ^TM 1079.

An example of a commercially available aliphatic epoxide is vinylcyclohexane dioxide, such as ERL-4206, ERL-4221, ERL-4201, ERL-4289, or ERL manufactured by Union Carbide Corp. -0400.

-- Phenolic resin, for example: Epi-Rez ^TM 5132 from Celanese, ESCN-001 from Sumitomo Chemical Co., CY-281 from Ciba Geigy, DEN ^TM 431 from Dow Chemical, DEN ^TM 438, Quatrex 5010 RE 305S manufactured by Kayaku Corporation of Japan, Epiclon ^TM N673 manufactured by Dainippon Ink and Chemical Co., Ltd., and Epikote ^TM 152 manufactured by Shell Chemical Co., Ltd.

- melamine resins, for example, produced by Cytec Cymel ^TM 327 and Cymel ^TM 323.

- terpene phenol tree, e.g. Arizona Chemical Company NIREZ ^TM 2019.

-- Phenolic resins such as YP 50 manufactured by Toto Kasei Co., Ltd., PKHC manufactured by Union Carbide Corp., and BKR 2620 manufactured by Showa Union Gosei Corp.

-- Soluble phenolic resins, especially combinations of soluble phenolic resins with other phenolic resins.

- polyisocyanates, for example, Japanese Polyurethane Ind produced Coronate ^TM L, Bayer (Bayer) produced Desmodur ^TM N3300 or Mondur ^TM 489..

In order to optimize the adhesive properties and activation range of the adhesive, a resin for improving adhesion (so-called viscous resin or tackifier) can be selectively added. The following are a few examples: hydrogenated and unhydrogenated derivatives of rosin, polyterpene resins (preferably polydecene resins based on α-pinene), terpene phenol resins, uncrosslinked phenolic resins, Novolac, hydrogenated and unhydrogenated polymeric product of dicyclopentadiene, hydrogenated and unhydrogenated polymeric product of C8 and C9 aromatics, hydrogenated C5/C9 polymeric product, aromatically modified selectively hydrogenated dicyclopentadiene a derivative, a resin based on a pure aroma (for example, α-methylstyrene, vinyltoluene, styrene), a resin composed of a mixture of different aromatic monomers, a benzofuran-oxime extracted from coal tar Resin.

The above-mentioned viscous resin may be used singly or as a mixture of two or more kinds of viscous resins.

The viscous resin selected is preferably such that the adhesive has no or only very weak tack at room temperature until tack is generated upon exposure to heat. It is preferred to manufacture the heat-activated adhesive film by selecting a resin having a high melting point (especially a resin having a softening temperature significantly higher than 110 ° C), wherein the softening temperature of the resin is replaced by a resin in accordance with DIN EN 1427:2007 The bitumen is measured; if the softening temperature is higher than 150 ° C, the measurement should be carried out in accordance with the provisions of 8.1b of this specification. It is also possible to use a low melting point resin, but it can be used only in a small amount, and the proportion of the total weight of the adhesive (excluding the conductive particles) is preferably less than 30% by weight.

Preferably, a crosslinkable adhesive is applied to the adhesive film of the present invention, especially an adhesive which is crosslinked by heat.

In order to produce crosslinks, a chemical crosslinker (also known as a hardener) may be added to the adhesive, especially a chemical crosslinker capable of reacting with at least one of the reactive resins. It is not necessary to add a crosslinking agent to produce a crosslinking reaction, but the crosslinking agent can capture excess reactive resin. In particular, when an epoxy resin is used as the active resin, it is an advantageous method to add a crosslinking agent.

The following are compounds that can act as crosslinkers/hardeners (for example, US 39700608 A for further explanation of these compounds):

-- a polyvalent aliphatic amine such as triethylenetetramine

-- a polyvalent aromatic amine such as isophorone diamine

-- 胍, such as dicyandiamide

-- Polyvalent phenol

-- Polyvalent alcohol

-- Multivalent mercaptan

-- Multivalent carbonic acid

-- Anhydride with one or more anhydride groups

In order to increase the reaction rate of the crosslinking reaction, a so-called accelerator may be added.

Here are a few examples of accelerators:

-- a tertiary amine such as benzyldimethylamine, dimethylaminomethylphenol

-- Tris(dimethylaminomethyl)phenol

-- Boron trihalide-amine complex

-- substituted imidazole

-- Triphenylphosphine

If a phenol resin (especially an alkylphenol resin) is used, a formaldehyde providing agent such as hexamethylenetetramine may be added.

In order to adjust the characteristics of the adhesive (especially the heat-activated adhesive), fillers (for example, (non-conductive) fibers, carbon black, zinc oxide, titanium dioxide, chalk, solid or hollow beads, other materials can be added. Microspheres (tannic acid, hydrazine hydrochloride), seed formers, bulking agents, tackifying additives thermoplastics, compounding agents and/or anti-aging agents (eg primary and secondary antioxidants or photoprotectants).

The following are some examples of other additives: primary antioxidants such as sterically hindered phenols, secondary antibodies such as phosphites or thioethers, process stabilizers such as C free radicals, photoprotectants such as UV rays Absorbent or sterically hindered amine, anti-odor oxidant, metal deactivator, processing aid.

Experiments have shown that the addition of a mixture of dendritic metal particles and conductive fibrous particles is much better than the effect of adding only one of the particles.

If only dendritic particles are added, the surface of the tape will become rough and most of the particles will protrude from the adhesive, making the agent unable to flow smoothly.

Fibrous particles are aligned when the tape is produced from the solution, and are preferably aligned with the track. Therefore, the conductivity in this direction is much higher than the direction of the right angle. In addition, the conductivity in the z direction is significantly smaller than in the case of using dendritic particles.

One surprising finding is that even without increasing the total amount of conductive particles, mixing the two particles together can be much better than using only one particle (fibrous or dendritic). The conductivity in the z direction is still very good (compared to the use of dendritic particles only), this has not changed. The conductivity in the x-y direction is still as good as when only fibrous particles are used, although the difference in orbital direction and right angle direction is still small. Only a small amount of dendrites are required to obtain a significant improvement in the laminability and adhesion of the adhesive.

It is even possible to reduce the total content of the particles and not to significantly reduce the conductivity in the x direction.

The structure of a conductive particle added by the adhesive film of the present invention has an anisotropic and multi-branched morphology, and a small branch (secondary crystal fork) protrudes from a trunk (primary crystal fork), and then from the second stage The fork extends a smaller branch (three-stage crystal fork). Branches can be straight or curved, and each branch can be subdivided into smaller branches, like St. Like a Christmas tree. The literature and the present specification refer to such particles as "dendritic crystals", "dendritic particles", "particles with dendritic shapes", or "particles with dendritic structures".

The length of the particles in one dimension will generally be greater than the length in at least one other dimension, especially greater than the length in the other two dimensions.

The dendritic particles used in the present invention are fine particles having at least a secondary crystal fork structure, and are preferably fine particles having at least a tertiary crystal fork.

The dendritic particles used are preferably composed of metal particles, and the following are a few examples: zinc, iron, bismuth, copper, silver, gold. Depending on the environmental conditions, metal particles that do not fail due to oxidation after a short period of time should be selected. It is preferred to use copper dendrites or gold dendrites. Gold works well but is very expensive. In order to utilize the high conductivity and high oxidation resistance of silver, and it is not necessary to bear a very high cost, it is preferred to use silver-plated copper dendrites in which the copper is preferably entirely covered by the silver plating. The amount of silver required to cover the copper depends on the size of the particles. Particles having a particle size between 30 μm and 40 μm require approximately 20% silver.

The maximum length of dendrites of different sizes is preferably approximately equivalent to the thickness of the adhesive film. In an advantageous manner, the average maximum length of the dendrites is between 20 μm and 100 μm, or preferably between 40 μm and 80 μm.

The second conductive particles in the adhesive film of the present invention have a fibrous structure. The length of the fibrous particles on a preferred side is much greater than the length in either direction perpendicular to the preferred direction. In an advantageous manner, the maximum length of the nits used is at least 3 times the maximum length in the direction perpendicular to the maximum length.

Fibers of smaller size should be selected, while the length of the fibers (maximum length of fibrous particles) should not be greater than 10 times the thickness of the adhesive layer. Particles having a length not greater than 5 times the thickness of the adhesive layer should be used, preferably particles having a length not greater than twice the thickness of the adhesive layer, or preferably not more than 1.5 times the thickness of the adhesive layer.

It is possible to use fibrous particles directly made of metal, or preferably metalized fibers, especially metallized glass fibers. Metallized carbon fibers can also be used. Preferably, the metal layer covers at least a substantial portion of the surface of the material contained therein, or preferably covers the entire surface of the material contained therein.

The outer surface (at least the majority of its surface) of the fibrous particles used preferably contains the same metal as the dendrites on at least a majority of its surface to avoid localized electrical corrosion, resulting in decomposition of the metal.

It is preferred to use a mixture of silver plated copper dendrites and silver plated glass fibers.

The ratio of dendrites to fibers can vary, but in the total weight of the conductive particles, the weight of either of the two particles should not be 10 times greater than the other particles. A particularly advantageous way is that the fibers and dendrites each account for half the weight.

The ratio of conductive particles (dendrites and fibers) to the total weight (adhesive plus particles) is between 40 and 90% by weight, preferably between 50 and 80% by weight, or most Good is between 55 and 70% (by weight).

The adhesive film of the invention is used for bonding work in the electronic field. Very good performance, such as bonding work for printed circuit boards.

The thickness of the adhesive film of the present invention is preferably between 30 μm and 100 μm, or preferably between 40 μm and 50 μm.

Experimental part: Bonding the FCCL with the finished tape

FCCL (soft copper foil) Pyralux LF9110R (1 oz Cu/) + (25 μm adhesive) + (25 μm kapton film) was bonded to steel ribs using a tape manufactured according to the example. At the same time, a tape of 1.5 cm in width was laminated on a polyimide film of FCCL composed of a polyimide/copper film at a temperature of 100 ° C, wherein the tape was slightly shorter than the FCCL to be bonded so as to have a grip afterwards. At the office. This composite of FCCL and tape was then laminated to a steel rib at a temperature of 100 ° C and the entire composite was placed in a heatable Buerkle press at a temperature of 180 ° C to 1.3 The pressure of Mpa is pressed for 20 minutes.

L-peeling test with FCCL-reinforced reinforced composites [IPC-TM-650 Nr. 2.4.9]

Using a tensile testing machine manufactured by Zwick, the FCCL of the FCCL and steel composite prepared in the above manner was peeled off from the rib at a speed of 50 mm/min and an angle of 90 degrees, and the required force was measured ( Unit: N/cm).

resistance

The resistance is measured in the manner specified by the military specification MIL-DTL-83528C.

Z-direction resistance

The adhesive film was removed from the existing release film or release paper and cut into a sample having an area of 5 x ⁵ cm ² . The test body is then placed between two cylindrical gold-plated electrodes previously cleaned with ethanol, both of which have a circular contact area of 1 square inch (one front side of the circular electrode), and Both electrodes are connected to a current-voltage source and a sensitive resistor meter. In this case, the adhesive film is horizontally located between the same horizontal contact faces. The lower electrode is located on a hard surface farther from the adhesive film. A 5 kg weight is then placed on the side of the upper electrode that is farther away from the adhesive film to provide good electrical contact to the adhesive film. The measurement was carried out in an environment of 23 ° C and a relative humidity of 50%. The measured resistance is in ohms.

Resistance in the x-y direction (surface resistance)

The uncrosslinked adhesive film was removed from the existing release film or release paper, and cut into a sample having an area of 5 x ⁵ cm ² . The measurement was performed using the measuring device as shown in Fig. 1. Where: V represents the voltage source

I stands for power

K stands for the adhesive film test body

1 represents gold-plated electrode

2 represents the insulator

X1 and x2 represent the length and width of the middle surface of the electrode, respectively

After the electrode was washed with ethanol, the electrode was placed on the test piece. The area between the two electrodes is exactly 1 square inch (6.45 mm ² ). The measurement was carried out in an environment of 23 ° C and a relative humidity of 50%. The electrode structure (including the electrode and the insulator) weighed 240 g.

The measured resistance is in ohms.

In order to distinguish the preferred direction, the test piece is placed once in the x direction and the y direction, and the measurement is performed, wherein the x direction is the direction of the coating, and the y direction is the direction perpendicular to the coating direction.

example Example 1:

66.5% by weight of Breon N41H80 (19% acrylonitrile-containing nitrile rubber, manufacturer: Zeon), 33% (by weight) of Epiclon 660 (novolac, manufacturer: DIC), and 0.5% (weight) Percentage of 2-phenylimidazole (based on solids; added to butanone at a concentration of 30%) was placed in a kneading machine to make a suspension. The kneading time is 20 hours.

Next, 30 parts (by weight) of solid adhesive composition, 35 parts of dendritic silver-plated copper particles (SC25D20 manufacturer: Spotters) and 35 pieces of silver-plated glass fiber (SATAR SHIELD AG 5512 Fl with a maximum length of 40 μm , Manufacturer: Nanotechnologies) added to the suspension.

The heat activated adhesive was then applied to a deuterated PET film and dried at a temperature of 100 ° C to form a 40 μm thick adhesive layer.

Comparative Example 2:

70 parts of dendrites were added to replace the mixture of fibers and dendrites.

Comparative Example 3:

70 parts of fiber were added to replace the mixture of fibers and dendrites.

result:

It is interesting to note that Comparative Example 2 is difficult to laminate on FCCL. Example 1 is very easy to laminate on FCCL. Nevertheless, contrary to Comparative Example 3, similarly good electrical conductivity was obtained.

Example 4:

66.5% by weight of Breon N41H80 (19% acrylonitrile-containing nitrile rubber, manufacturer: Zeon), 33% (by weight) of Epiclon 660 (novolac, manufacturer: DIC), and 0.5% (weight) Percentage of 2-phenylimidazole (based on solids; added to butanone at a concentration of 30%) was placed in a kneading machine to make a suspension. The kneading time is 20 hours.

Next, add 40 parts of solid adhesive, 30 parts of dendritic silver-plated copper particles (SC25D20 manufacturer: Spotters) and 30 pieces of silver-plated glass fiber (SATAR SHIELD AG 5512 Fl, manufacturer: Nanotechnologies) with a maximum length of 40 μm . Into the suspension.

The heat activated adhesive was then applied to a deuterated PET film and dried at a temperature of 100 ° C to form a 40 μm thick adhesive layer.

Comparative Example 5:

Add 60 parts of dendrites to replace fibers and dendrites a mixture of crystals.

Comparative Example 6:

60 parts of fiber were added to replace the mixture of fibers and dendrites.

result:

It can be seen from the above examples of adding a smaller amount of fine particles that it is very advantageous to add a mixture of dendrites and fibers because only a combination of the two can achieve high electrical conductivity in all three directions and/or very Low resistance.

V‧‧‧ represents the voltage source

I‧‧‧ represents the power source

K‧‧‧ represents the adhesive film test body

1‧‧‧ represents gold-plated electrodes

2‧‧‧ represents insulator

X1 and x2‧‧‧ represent the length and width of the middle face of the electrode

Figure 1 shows the measuring device.

Claims (9)

An adhesive film comprising a layer of an adhesive and conductive particles doped in the adhesive, wherein one part is fibrous conductive particles and the other part has a dendritic structure. For example, the adhesive film of claim 1 is a heat-activatable adhesive. The adhesive film according to any one of the preceding claims, wherein the metal fibers and/or the metallized fibers are used as the fibrous conductive particles. The adhesive film according to any one of the preceding claims, wherein the metal particles and/or the metallized particles are used as dendritic conductive particles. The adhesive film according to any one of the preceding claims, wherein the surface of the fibrous conductive particles and the surface of the dendritic conductive particles are composed of the same material. The adhesive film according to any one of the preceding claims, wherein silver-plated copper particles are used as dendritic conductive particles, and silver-plated glass fibers are used as fibrous conductive particles. The adhesive film according to any one of the preceding claims, wherein the maximum length of the fibrous conductive particles is not more than 10 times the thickness of the adhesive layer, preferably not more than 5 times the thickness of the adhesive layer, and most preferably no more than adhesive. 1.5 times the thickness of the agent layer. The adhesive film according to any one of the preceding claims, wherein all of the conductive particles constitute 40 to 90% by weight based on the total weight of the adhesive film. The adhesive film according to any one of the preceding claims, wherein the weight ratio V of the fibrous conductive particles to the dendritic conductive particles is between 10:1 and 1:10, preferably 1:1.